The purpose of the Bone Biology Core (Core B) is to provide a standardized set of bone assay services that will facilitate completion ofthe broader goals and objections ofthe Program Project goals and specific aims. The objective of this Program Project application is to understand how age-associated changes in nutrient-related factors alters the environmental milieu of stem cells in bone. Each ofthe three projects investigates different aspects ofthese nutrient-related signals, yet all will employ similar techniques and animal models. The Bone Biology Core will provide each investigator with standard assay services in the areas of bone histology and histomorphometry, imaging, densitometry, biomechanics, and serum biochemistry. Dr. Mark Hamrick will be the core director. He is a bone biologist with experience and expertise in the areas of bone histomorphometry, densitometry, and biomechanics with particular emphasis on the use of animal models in bone metabolism research. He will be responsible for overseeing all administrative issues related to the Core B fadlities, as well as supervising the collection, preparation, and distribution of bone specimens. The Core will serve as the major center for data collection related to bone metabolism, and as such represents a key component linking the individual projects. Moreover, the Core seeks to develop new technologies in support of future research activities related to the objectives of the Program Project grant.